Hello LLVM Devs,
I am trying to compile following simple program for an experimental backend
int main()
{
printf(“Hello World \n”);
return 0;
}
I have added code to lower return instruction in the backend however in assembly I don’t find return instruction generated.
In the debug-only=isel dump I can see that my target specific SDNode for RET_FLAG is added but it gets removed during DAG
optimization phase.
Initial selection DAG: BB#0 ‘main:entry’
SelectionDAG has 18 nodes:
t5: i32 = GlobalAddress<i32 (i8*, …)* @printf> 0
t0: ch = EntryToken
t4: ch = store<ST4[%retval]> t0, Constant:i32<0>, FrameIndex:i32<0>, undef:i32
t8: ch,glue = callseq_start t4, TargetConstant:i32<0>
t10: ch,glue = CopyToReg t8, Register:i32 %R5, GlobalAddress:i32<[14 x i8]* @.str> 0
t12: ch,glue = DummyArchISD::CALL t10, TargetGlobalAddress:i32<i32 (i8*, …)* @printf> 0, Register:i32 %R5, t10:1
t13: ch,glue = callseq_end t12, TargetConstant:i32<0>, TargetConstant:i32<0>, t12:1
t15: i32,ch,glue = CopyFromReg t13, Register:i32 %R3, t13:1
t16: ch,glue = CopyToReg t15:1, Register:i32 %R3, Constant:i32<0>
t17: ch = DummyArchISD::RET_FLAG t16, Register:i32 %R3, t16:1
t15: i32,ch,glue = CopyFromReg t13, Register:i32 %R3, t13:1
Optimized lowered selection DAG: BB#0 ‘main:entry’
SelectionDAG has 15 nodes:
t0: ch = EntryToken
t4: ch = store<ST4[%retval]> t0, Constant:i32<0>, FrameIndex:i32<0>, undef:i32
t8: ch,glue = callseq_start t4, TargetConstant:i32<0>
t10: ch,glue = CopyToReg t8, Register:i32 %R5, GlobalAddress:i32<[14 x i8]* @.str> 0
t12: ch,glue = DummyArchISD::CALL t10, TargetGlobalAddress:i32<i32 (i8*, …)* @printf> 0, Register:i32 %R5, t10:1
t13: ch,glue = callseq_end t12, TargetConstant:i32<0>, TargetConstant:i32<0>, t12:1
t15: i32,ch,glue = CopyFromReg t13, Register:i32 %R3, t13:1
Can someone please guide me how to furhter debug this situation? Or any hints.
Sincerely,
Vivek